1. Field of the Invention
The present invention relates to improvements to an immersion device, in which a workpiece such as a semiconductor wafer is immersed into a chemical and cleaned.
2. Description of the Prior Art
In production of semiconductor devices such as LSI, various kinds of fine particle dust is generated due to various reasons. For example, there are process dust caused in the process of diffusion, CVD or ion injection, and mechanical dust caused in the process of handling, storage or transportation. When such fine particle adheres to semiconductor wafer, that greatly affects production yield of semiconductor device. Accordingly, the semiconductor wafer must be cleaned in production of the semiconductor device. Generally 5-10 processes are repeated for the cleaning process of the semiconductor wafer. In the cleaning method, there are wet-type cleaning device which removes dirt using liquid such as chemical or pure wafer, and dry-type cleaning device which uses no liquid. An immersion cleaning device can clean all of various particles with low cost, and effectively. FIG. 1 shows the immersion cleaning device as an example of former wet-type cleaning device. In the figure, an immersion cleaning device 1 is composed of ceiling portion 1a, cleaning bath portion with a plurality of cleaning bath (chemical bath or pure water bath) 10b, loader portion 1c, unloader portion 1d and work transportation portion 1e. Specified number of magazine If mounted with semiconductor wafer is put on loader portion. Upon this, when cleaning conditions is inputted into controller 1g, work transportation portion 1e chucks magazine 1f with clicks 1i, puts it into cleaning bath 10b and cleans semiconductor wafer, and semiconductor wafer is dried at IPA (isopropyl alcohol) vapor drier 1h situated at unloader portion 1d. When cleaning treatment is completed, controller 1g inform operator of the completion. As sequence of cleaning treatment for semiconductor wafer, there are, for example, the following: heated concentrated nitric acid--pure water--heated cencetrated sulfuric acid --pure water--dilute hydrofuluoric acid--pure water--IPA drier; (ammonia water+hydrochloric acid)--pure water dilute hydrofluoric acid pure water IPA vapor drier. When the device, as shown in FIG. 1, has a plurality of work transportation portion 1e, range of cleaning bath 1b, which each work transportation portion 1e takes charge of, is specified, and each transportation portion 1e takes the magazine 1f into and from the cleaning bath. (Upon this, cleaning bath ranges, which neighboring work transportation portion 1e takes charge of, partially lap.)
There is sometimes an immersion cleaning device, in which, to prevent contamination due to fine particle on semiconductor wafer and mist, clean air having passed through high performance filter is flowed downward from ceiling portion 1a to be exhausted through exhaust hole (exhaust means) 1j, and by this, inside of the immersion cleaning device 1 is kept clean and gas generating from cleaning bath 10b is suppressed. In reference to FIG. 2, an example of a cleaning process in such device for semiconductor wafer is still explained in detail. Each cleaning bath 10b-10b-3 is housed in concave portions formed on upper surface of the cleaning portion 1b. To begin with, magazine 1f is immersed for 10 min. in heated concentrated nitric acid bath 10b-1. Then, work transportation portion 1e holds the magazine 1f and transports it to pure water bath 10b-2. After cleaning semiconductor wafer for 110 min. in the pure water bath 1b2, the work transportation portion 1e again holds the magazine 1f and transport it to dilute fluoric acid bath 10b-3 3 to immerse it for 5 min.. Then, the work transportation portion 1e again transport the magazine 1f to the following bath. In this way, the magazine is put in or taken out from chemical bath to clean semiconductor wafer in the magazine. Upon this, clean air 1k blown out from ceiling portion 1a is exhausted by exhaust means 1m through exhaust hole 1j together with gas generating from each cleaning bath 10b. In the figure, clean air 1k is shown only above the cleaning bath 10b-2, but the cleaning air is generally blown out over the entire cleaning bath portion 1b from ceiling portion 1a. In the case of the above device, almost all gases generating from cleaning bath (for example, cleaning bath 10b-3 in FIG. 8), in which magazine 1f mounted with semiconductor wafer as work is completely immersed, and generating from cleaning bath (for example, cleaning bath 10b-1), in which magazine 1f is not immersed, are exhausted through each hole 1j. However, gas generating from chemical adhering to magazine 1f or to semiconductor wafer (work), during transportation (for example, as shown in the above of clearing bath 10b-2 in FIG. 2), is not completely absorbed through exhausted hole 1j and stirred by clean air 1k blown out from ceiling portion 1a. In addition, when chemical is heated, the specific gravity becomes less than air, so that the gas is scattered in upper or side direction going counter flowing direction of the clean air 11k. In this case, part of chemical combines with moisture in the air to become mist, and is scattered to outside of the immersion cleaning device 1 together with gas. Gas or mist generating from chemical is often acid or alkaline. Accordingly, if such gas or mist is scattered to outside of the immersion cleaning device is not only corrodes or deteriorates surrounding parts, but also gives unfavorable effects to human bodies.
In addition, in the case of above device in which clean air is blown out, part of scattered gas or mist is again taken into the high performance filter at the ceiling portion 1a together with room air and circulates through the device and concentrates in proportion to operation time. As result, the high performance filter and motor fan are corroded. Beside, if the work transportation portion 1e and senser system of the device are corroded, operation error of the device is sometimes caused. This not only leads to poor cleaning and damage of the semiconductor wafer, but also dangerous to an operator. Conventional device has the above problems.